Effect of Microstructural Variation of a Martensitic Stainless Steel on High Temperature Degradation Behavior

Abstract

: Martensitic stainless steels are chromium steels with a small addition of Ni. They have a good combination of mechanical properties and corrosion resistance, due to their Cr content [12]. The degradation processes are present in several industrial equipments and, generate repair or replacement actions in a periodic way. In an attempt to minimize these problems, several studies have been developed with this purpose. However, due to the several variables involved in the process, both in design and equipment operation, there is still a fertile field for an effective understanding of these degradation problems. For example, one can cite the effects that the different microstructures developed in martensitic stainless steels, materials commonly used in severe service conditions, present on the behavior of resistance to oxidation of the material. And, also, the environment in which the material is inserted. In a high-temperature environment, impurities are found, among them, compounds such as vanadium pentoxide, which act vigorously in the progression of the oxidation process. Oxidation tests are necessary to relate the behavior and influence exerted on the oxide layer by grain refinement. Thus, the present work aims to analyze the influence of the microstructure of the martensitic stainless steel AISI 420, with application of different treatments. The behavior of this steel was evaluated under different oxidation conditions, in contact with a solution containing Vanadium Pentoxide, and as a control parameter the mass variation of the samples. Analysis of the microstructures and the corrosion/oxidation products were carried out via Optical Microscopy, Scanning Electron Microscopy. As result it was verified the importance of the microstructure in the material's resistance to the action of degradation by oxidation, and its influence on the oxide layer formation process.